22  Unit 5: Blizzards 5E

How do severe winter storms form, and could they become worse in the future?

Author

Earth & Space Science

HS-ESS2-8 Time: 7–13 Days

🌨️ Winter Storm Jonas: Anatomy of a Blizzard 🌨️

23 Engage: The Investigative Phenomenon

23.1 ❄️ Winter Storm Jonas (January 22–24, 2016)

Winter storm Jonas produced strong enough winds and enough snow to cause significant disruptions to society, damage to property, and harm to human life.

Quick Facts:

  • πŸ“ Up to 40 inches of snow in parts of West Virginia
  • πŸ’¨ Wind gusts exceeding 60 mph along the coast
  • πŸ™οΈ New York City received 27.5 inches β€” near-record snowfall
  • ⚑ Over 300,000 power outages across the Mid-Atlantic
  • πŸ’° Estimated $3 billion in damages
  • 😒 At least 55 deaths attributed to the storm

23.1.1 πŸ€” Driving Questions:

  • What causes the wind associated with a blizzard?
  • What causes the snow and precipitation during a storm like this?
  • Could storms like Jonas become more common or more intense?

23.1.2 πŸ“ Notice & Wonder

Before we dive into the science, take 3 minutes to write:

  1. What do you notice about Winter Storm Jonas?
  2. What do you wonder about how storms like this form?
  3. Have you personally experienced a storm like this? What was it like?

24 Explore: What Causes Wind?

24.1 πŸ”¬ Investigation: Pressure & Wind

Wind isn’t random β€” it has a cause. In this section, you’ll build a model of what creates wind and why it blows in specific directions.

24.2 The Wind Machine: Pressure Differences

Wind is caused by differences in air pressure. Air always moves from areas of high pressure toward areas of low pressure. The greater the pressure difference, the stronger the wind.

But what causes pressure differences? Uneven heating of Earth’s surface.

24.2.1 πŸ’‘ Key Concept: What Drives Wind

Uneven heating β†’ Temperature differences β†’ Pressure differences β†’ WIND

  1. When the Sun heats Earth’s surface unevenly, some areas become warmer than others.
  2. Warm air is less dense and rises, creating an area of low pressure at the surface.
  3. Cool air is more dense and sinks, creating an area of high pressure at the surface.
  4. Air flows from high pressure β†’ low pressure. This is wind!
  5. The greater the pressure difference (the pressure gradient), the faster the wind.

24.2.2 πŸ“ Explore Activity

Use the sliders above to investigate:

  1. Set the left region to 310 K and the right to 270 K. What happens to wind speed?
  2. Now bring them closer together (290 K and 280 K). How does wind speed change?
  3. What temperature combination creates the strongest wind?
  4. In your own words, explain why uneven heating causes wind.

24.3 Air Masses: The Building Blocks of Weather

An air mass is a large body of air (covering thousands of square miles) that has relatively uniform temperature and humidity. Air masses form when air sits over a region long enough to take on that region’s characteristics.

24.3.1 πŸ’‘ Key Concept: Air Mass Classification

Air masses are classified by two properties:

Symbol Temperature Source Humidity Source
c (continental) Forms over land β†’ dry
m (maritime) Forms over water β†’ moist
A (Arctic) Very cold regions
P (Polar) Cool mid-latitude regions
T (Tropical) Warm low-latitude regions

So mT = maritime Tropical = warm and moist (like air from the Gulf of Mexico), and cP = continental Polar = cool and dry (like air from Canada in winter).

25 Explore: Fronts β€” When Air Masses Collide

25.1 πŸŒͺ️ What Happens When Air Masses Meet?

When two air masses with different properties meet, they don’t mix easily. The boundary between them is called a front. Fronts are where weather happens!

25.2 Types of Fronts

25.2.1 πŸ“ Front Analysis

Use the dropdown above to explore each front type. For each one, answer:

  1. Which air mass is advancing?
  2. What happens to the warm air?
  3. What type of precipitation would you expect (brief and intense, or steady and prolonged)?
  4. Which front type is most associated with blizzards?

26 Explain: How Do Blizzards Form?

26.1 🧊 Building a Blizzard Model

Now that you understand wind (from pressure differences) and precipitation (from air mass collisions at fronts), let’s put it all together to explain how blizzards form.

26.2 The Mid-Latitude Cyclone

Blizzards are produced by powerful mid-latitude cyclones β€” large low-pressure systems that form at the boundary between polar and tropical air masses, typically between 30Β°N and 60Β°N latitude.

26.2.1 πŸ’‘ Key Concept: Mid-Latitude Cyclone β†’ Blizzard

A blizzard is a severe mid-latitude cyclone that produces:

  • Heavy snow (reduces visibility to less than ΒΌ mile)
  • Strong winds (sustained 35+ mph for 3+ hours)
  • Cold temperatures (usually below 20Β°F)

These conditions occur on the cold side of the low-pressure center (north and west of the center in the Northern Hemisphere), where cold, dry polar air wraps around the system and collides with moist air being lifted along the fronts.

26.3 Reading Weather Maps

Meteorologists use surface analysis maps to track air masses, fronts, and pressure systems. Understanding these maps is key to predicting blizzards.

26.3.1 πŸ—ΊοΈ Weather Map Symbols

Symbol Meaning
L (red) Low-pressure center β€” rising air, clouds, precipitation
H (blue) High-pressure center β€” sinking air, clear skies
Blue line with triangles β–² Cold front (triangles point in direction of movement)
Red line with semicircles β¦Ώ Warm front (semicircles point in direction of movement)
Alternating blue/red Stationary front
Purple line with both Occluded front
Concentric circles Isobars β€” lines of equal pressure (closer = stronger wind)

26.3.2 πŸ”¬ Lab Activity: Track Winter Storm Jonas

Using the NOAA Weather Prediction Center’s archived surface analysis maps:

  1. Find surface analysis maps for January 21–24, 2016
  2. For each day, identify:
    • Location of the low-pressure center
    • Types of fronts present
    • Which air masses are interacting
    • Where precipitation is falling
  3. Create a timeline showing how the storm developed, reached peak intensity, and dissipated
  4. Compare the storm’s lifecycle to the mid-latitude cyclone stages above

Resources: NOAA Weather Prediction Center Archive

27 Explain: Precipitation β€” Where Does Snow Come From?

27.1 πŸ’§ From Water Vapor to Snowflakes

Understanding precipitation requires connecting energy, water, and air movement. Let’s trace the journey from evaporation to snowfall.

27.2 The Precipitation Process

27.2.1 πŸ’‘ Key Concept: Why Fronts Produce Precipitation

  1. Warm, moist air (often from the Gulf of Mexico) contains lots of water vapor
  2. At a front, this warm air is forced upward over cold air
  3. As air rises, it cools (because atmospheric pressure decreases with altitude)
  4. Cool air holds less water vapor than warm air
  5. Excess moisture condenses into water droplets or freezes into ice crystals
  6. When crystals grow heavy enough, they fall as snow (if temperatures remain below freezing all the way to the ground)

❄️ A single mid-latitude cyclone can lift BILLIONS of tons of moist air, producing enough snow to bury an entire state! ❄️

28 Elaborate: Blizzards & Climate Change

28.1 🌑️ Will Blizzards Get Worse in a Warming World?

This might seem like a contradiction β€” how can global warming lead to bigger snowstorms? Let’s investigate with data.

28.2 The Paradox: More Warming β†’ More Snow?

It sounds counterintuitive, but a warmer atmosphere can actually fuel more intense winter storms in some regions. Here’s why:

29 Evaluate: Putting It All Together

29.1 βœ… Assessment: Build Your Blizzard Model

You now have all the pieces to explain how blizzards form and how they may change with climate change. Let’s check your understanding!

29.1.1 🧠 Check Your Understanding

Question 1: What is the fundamental cause of wind?

Question 2: In a mid-latitude cyclone, blizzard conditions (heavy snow, high winds) are most likely found:

Question 3: How can climate change lead to more intense blizzards even as average temperatures rise?

29.1.2 πŸ“ Culminating Task: Blizzard Explanation Model

In your notebook, create a visual model (diagram + written explanation) that answers:

β€œHow did Winter Storm Jonas produce strong enough winds and enough snow to cause significant disruptions?”

Your model should include: 1. The air masses that interacted (with sources and properties) 2. The fronts that formed and how they caused precipitation 3. The mid-latitude cyclone structure and how it generated strong winds 4. An explanation of the energy source driving the storm 5. A claim about whether storms like Jonas could become more common, supported by evidence about atmospheric moisture and jet stream changes

Use the vocabulary: pressure gradient, air mass, front, mid-latitude cyclone, adiabatic cooling, condensation, Clausius-Clapeyron, Arctic amplification

30 Summary: Key Takeaways

Concept Key Idea
Wind Caused by pressure differences from uneven heating
Air Masses Large bodies of air with uniform temp & humidity
Fronts Boundaries between air masses; where weather happens
Mid-Latitude Cyclone Low-pressure system with warm & cold fronts; produces blizzards
Precipitation Warm moist air rises at front β†’ cools β†’ condenses β†’ snow/rain
Climate Connection Warmer air holds more moisture + weakened jet stream = potentially more intense blizzards

Next up: We’ll investigate why storms follow the paths they do β€” and whether those paths are changing. πŸ—ΊοΈ